Liquids administered by intravenous injection, such as whole blood, plasma, saline and dextrose solutions, are typically supplied in disposable infusion bags which are most often made of a flexible, transparent plastic having an outlet port or delivery tube which is adapted to be punctured by a coupler of a recipient set. In use, the infusion bag is suspended above the patient and the liquid contained therein is permitted to flow by gravity into the patient's vein. There are many situations, particularly when the infusion bag is nearly empty or in cases of severe hemorrhage and shock, where the administration of fluid by gravity flow with conventionally employed infusion bags is unacceptably slow.
Various pressure infusion apparatus have been used in the past to overcome such problems of slow delivery. See, for example, U.S. Pat. No. 2,766,907, issued to Wallace, Jr.; U.S. Pat. No. 3,153,414, issued to Beall et al.; U.S. Pat. No. 4,090,514, issued to Hinck et al.; U.S. Pat. No. 4,507,116, issued to Leibinsohn; and U.S. Pat. No. 4,735,613, issued to Bellin et al. Such known pressure infusion apparatus characteristically comprises bladder means for maintaining a fluid under pressure, means forming a pocket with the bladder means for holding an infusion bag against the bladder means for pressurizing the infusion bag by transmission of pressure from the pressurized bladder means to the infusion bag, and pressurization means which is coupled to the bladder means for introducing a flow of the fluid into the bladder means and thereby pressurizing same. A conventional inflation, or "squeeze" bulb is typically used as a pressurization means to minimize manufacturing costs.
One problem with such inflation bulbs is their tendency to leak and, therefore, their inability to maintain pressure during use of the pressure infusion apparatus. Typically, inflation bulbs used with pressure infusion apparatus are of a "double-ended" type, such as the inflation bulbs which are shown in the above-referenced patents of Beall et al., Hinck et al., Leibinsohn and Bellin et al. These double-ended inflation bulbs are so called because they have one check valve at the distal end of the inflation bulb and another check valve at the proximal end of the inflation bulb. A squeezing of this type of inflation bulb simultaneously closes the distal end check valve while opening the proximal end check valve, and thereby creates a positive pressure for pumping air into the bladder means. When such inflation bulbs are released, the distal end check valve opens and the proximal end check valve closes to create a negative pressure until the inflation bulb is reinflated. Since the distal end check valve in such double-ended inflation bulbs is exposed to the ambient air, it can be readily appreciated that these check valves may leak.
Accordingly, it is desirable to use a single-ended inflation bulb having a check valve at the end, wherein the check valve has two valves, one valve for providing a passage for fluid flow from the inflation bulb to the bladder means during squeezes of the bulb, and a second valve for providing a passage for fluid flow from an intake port to the inflation bulb during releases of the bulb, in order to refill the bulb with air. Check valves are known, such as that disclosed in U.S. Pat. No. 4,437,490, issued to Demers et al, which comprise a dual valve assembly, wherein a flexible diaphragm provides for opening of one valve and simultaneous closure of the other valve, in order to alternately allow fluid flow through one valve and prevent fluid flow through the other valve. Such a valve comprises a flexible diaphragm which has flaps or reeds which provide for opening and closure of the fluid flow ports.
However, a problem has been recognized in that the use of flap or reed type diaphragms in dual flow check valves may be ineffective in some cases. The flaps are prone to curling and/or twisting, causing attendant leakage at the valve closures and tearing of the diaphragm material.
Therefore, there is a need for a single-ended inflation bulb for use in a pressure infusion system, wherein a flexible diaphragm effectively provides for closure of a specific valve and is not prone to the problems associated with flapping or curling. The present invention provides a check valve which satisfies this need.